Socket devices for baseless lamps such as incandescent lamps and light emitting diodes are widely used in audio and video instruments, meters for cars, liquid crystal displays, or displays for a controller used in plants. Those socket devices have such merits that supporting and electrical connections of the lamps can be easily made with a simple structure and a low cost when they are assembled on printed circuit boards.
The conventional socket device for baseless lamps is provided with a tubular main body, which is a bottomed cylinder made of electrically insulating material such as resin or rubber. The tubular main body has a lamp-loading hole having an opening at upper end, through which a baseless lamp is inserted. In the outer wall forming the lamp-loading hole, a pair of notches is formed, which extend downward along the tubular socket axis from the leading end of the hole. The pair of notches is arranged on the diametrically opposing positions of the lamp-loading hole. On the outer surface of the tubular main body, flange portion is also provided around the tubular main body at a prescribed distance from the lower ends of the pair of notches. A protrusion is also provided at a prescribed distance from the flange portion on the outer surface of the tubular main body. The protrusion is arranged at a position spaced from the notches in the circumferential direction of the outer surface of the tubular main body. Electrically conducting connecting members made of a metal plate are provided in the loading hole. Sealing portions of a wedge base type lamp is connected and is supported on the connecting members. A pair of terminal pieces is connected with the connecting member. These terminal pieces pass through the pair of notches and extrude on the outer side of the tubular main body.
The socket device is assembled after inserting the tubular main body having the protrusion into a socket assembly hole formed on a printed circuit board, by turning the main body with the printed circuit board sandwiched between the protrusion and the flange portion. At this time, the terminal piece is in contact with a wire conductor made of such a thin film as a copper foil formed on the surface of the printed circuit board, through which electricity is supplied to turn on the lamp.
Here, in one type of the socket device known to the public, the terminal piece is arranged to protrude at a position spaced from the flange portion, and to contact with wire conductors formed on an upper surface of the printed circuit board.
In the other type of the socket device also known to the public, the terminal piece is received in a concave portion formed in the flange portion, in order to contact with the wire conductors formed on an under surface of the printed circuit board.
In yet other type of the socket device known to the public, the above-mentioned two types are combined, in which a pair of terminal pieces is provided, which is contact with the both sides of the board, when the socket device is loaded on the printed circuit board.
In the conventional socket devices described, the terminal pieces are protruding from the outer surface of the main body of the socket device. Therefore, when a lot of the socket devices are put together into a container boxes while manufacturing, assembling or carrying, the terminal pieces protruding from the socket body contact with other socket devices or a wall of the container box, and sometimes they are deformed. If such deformation takes place in the terminal piece, insufficient contact between the terminal piece and the wire conductor of the printed circuit board occurs, and, in the worst case, it is impossible to assemble the socket device on the printed circuit board.
It is an object of the present invention to solve the above-mentioned problems, and to provide a socket device, in which the deformation of the terminal pieces extruding from the outer surface of the main body of the socket device is prevented and an electric connection is secured.